Dual Tone Multi-Frequency (DTMF) tones correspond to input keys on many communication devices. For example, the # key and the 8 key each have corresponding DTMF tones. In Voice over Internet Protocol (VoIP) communication systems, the DTMF tones are encoded into the VoIP packets. There are various forms of DTMF coding, such as International Telecommunications Union (ITU) G.711, Internet Engineering Task Force (IETF) Request For Comment (RFC) 2833, or Session Initiation Protocol (SIP) Information Messaging. If two communication systems on different sides of a VoIP call use different DTMF coding formats, then the DTMF signals must be transcoded from one DTMF coding format into another.
Session border controllers are located at the entry points of many VoIP networks. The session border controllers provide network security, address translation, and DTMF transcoding, among other features. Unfortunately, DTMF signaling is rarely used on the high volumes of VoIP calls. Thus, the DTMF transcoders sit idle in many session border controllers. In addition, the session border controllers may not support all of the possible DTMF transcoding combinations.
Overview
In a packet communication system, session border controllers receive and process communication packets to detect DTMF signaling. If the DTMF signaling is detected, then the session border controllers determine if DTMF transcoding is required. If the DTMF transcoding is required, then the session border controllers transfer DTMF transcoding instructions to a DTMF transcoding server. In response to the transcoding instructions, the DTMF transcoding server transfers transcoded DTMF signaling.